If you drive in congested areas only, then this is what you will get.
Mileage will improve when the car switches to EV mode on straight stretches.
Never the less I expect the car to give you around 15.
I suspect its the oil, the one poured in your car may not be 0w-20 which can effect the mileage surely.
If you can afford get the oil changed to 0w-20 Total, Shell or Kixx. with new oil filter.